The goal of this project is to study genes regulating the growth and differentiation of lymphocytes. Our approach has been to isolate genes which are specifically expressed in B or T lymphocytes through the technique of substracive hybridization (see Methods). We have concentrated on isolating genes encoding cell surface receptors or genes which can be studied in the context of mutations affecting lymphocyte development. We have been successful in isolating cDNA clones encoding the Alpha and Beta chains of the T cell's receptor for antigen. We have also defined an x-linked family of mouse genes which may be mutant in mice bearing the X-linked immunodeficiency, xid, and we have begun to define human equivalents to this gene.